“It can grow on the ground, it can also grow as a vine climbing up a tree,” said Amber Carothers, York County Park naturalist.

Carothers says poison ivy can be tough to identify, since each plant can have a different look. But a good rule of thumb is: Leaves of three, let it be.

“Typically the leaves that are on the outside kind of look like they have thumbs and the ones on the inside have pinkies and a thumb,” said Carothers.

A majority of people, including Susan Shapiro, are allergic to poison ivy.

Dermatologist George Groleau says it’s the oil from the plant that causes the itchy, burning rash.

“It will interact with your immune cells that are in your skin. If you are allergic, the reaction occurs,” said Dr. Groleau.

That oil can also get on your shoes, your garden gloves and tools. If you touch them, it can transfer to your skin.

“Now, the myth is that if you get the oil, within an hour you are OK. Well that’s going to totally depend on how allergic you are,” said Dr. Groleau.

It’s also a myth that scratching the blisters will spread the rash. It may pop up in different areas of your body over several days because of different sensitivity, and you can’t pass it to another person.